Piston expander



1935= c. F. JOHNSTON 2,010,518

PI STON EXPANDER Filed June 15, 1932 INVENTOR. Char/es F Johnsfon.

BY ATTORNEY Patented Aug. 6, 1935 UNITED STATES PATENT OFFICE 5 Claims.

The invention relates to a means associated with a piston for holding the skirt of the piston in an expanded relation whereby the latter may compensate for the concavities worn in the cylinder walls and resulting in what is generally known as piston slap. I

An object of the invention is to provide a means of the character described which will cause the skirt to be expanded solely in conformity with the deformation produced in the cylinder from such piston slap.

Another object of the invention is to provide a means of the character described which will afford the desired expansion of the piston skirt for the full length thereof Without requiringany departure from the design of the conventional type of piston.

Afurther object is to provide a piston skirt expanding means which may be absolutely locked in operative position on the piston without re-' quiring the provision of any attaching parts on the piston or the use of any attachments between the piston and the expander.

A still further object of the invention is to provide a means of the character described in which all portions thereof, including that for retairing the means on the piston, may be in the form of a single integral member.

The invention possesses other objects and features of advantage, some of which, with the foregoing, will be set forth in the following description of the preferred form of the invention which is illustrated in the drawing accompanying and forming part of the specification. It is to be understood, however, that variations in the showing made by the said drawing and description may be adopted within the scope of the invention as set forth in the claims.

Referring to said drawing:

Figure 1 is a longitudinal sectional view, partly in elevation, aha piston equipped with the expanding means of my invention.

Figure 2 is a perspective view of the piston and expander as viewed from the bottom of the piston and at a slight angle.

Figure 3 is a side elevation of the piston at right angles to that shown in Figure 1.

Figure 4 is a perspective view of the expander without the piston.

Figure 5 is a fragmentary perspective view.of the piston and a slightly modified form of the expander as viewed from the bottom of the piston at a small angle.

As illustrated in the drawing, the expander member 2 in the preferred embodiment of the invention is arranged for positioning on the inside of a piston 3 such as used in an internal combustion engine. More specifically the member 2 is arranged within the portion 4 of the piston, usually termed the skirt and which includes the sides of the piston extending to the open end 6.

The skirt 4 has formed therein, as clearly shown in Figure 2, a longitudinal slit 1 which extends from a point adjacent the ring retaining portion 5 of the piston to, the end 6. The slit 1 is disposed about mediately of the wrist-pin bearings 9 which are arranged in the piston in diametrically opposed relation. At the inner end of the slit and communicating therewith is a cross slit 8 which extends transversely and partially around the piston in opposite directions from slit 1.

As is well known, most of the wear on the engine cylinder walls occurs along the portions lying transversely of the wrist-pin axis, such as the surface engaged by the portion of the piston opposite that containing slit 1. After a certain amount of such wear, the cylinder becomes somewhat oval-shaped in cross section and piston slap, in a more or less aggravated degree, results. As an effective means of overcoming such looseness or slap 0f the piston, without reboring the cylinder, said side portion of the piston is caused to be expanded so that it may bear against the worn side of the cylinder to thereby cause the piston to be retained in a centralized position. To cause the piston to become expanded to the exact amount and form required, and to do this with a very simple means and in the efficacious manner above referred to, is one of the main-purposes of my invention.

As illustrated in Figures land 2, the expander member 2 is interposed between the slitted side of the piston skirt and the bearings 9, and the form of the member and its positioning in the piston is such as to force outwardly and evenly the two portions 12 of the skirt separated by slit 1. The member as aforesaid is desirably formed with all parts thereof in a single piece, and in the preferred embodiment is constructed of relatively heavy spring wire. Essentially the member in its present form comprises two parts, to Wit, a skirt expanding portion and a portion for retain- I ing the first portion operatively locked in position. More specifically, as clearly shown in Figure 4, the portion for expanding the skirt in- 50 eludes an outwardly-curved segment M which is designed for engagement with the inner face of the skirt at one or more points mediately of the bearings 9. Preferably the form of the segment 7 is such that points on each of the skirt portions 55 12 are engaged thereby, and, as is important to note, in order that said portions will be expanded in the desired manner, the contact between the segment and skirt portions is desirably adjacent slit 1. Furthermore in order to provide an ample bearingvbetween the segment and skirt portion, the engaging surface of the segment is curved somewhat in conformity with the inner circumference of the skirt. The segment is retained against the skirt by means of bearing engaging portions l5 and I6 which are in the form of legs extending laterally from the ends of the segment and disposed at nearly right angles thereto. The legs I 5 and it are designed to seat at the juncture of the bearings 9 and the contiguous side portion of the skirt or other appropriate part H on the inner side of the piston so that with a tension set up in the member 2 between the said juncture and the points of contact with the skirt portions l2, the latter will be expanded outwardly in proportion to the amount of the tension.

The member 2 is designed to contact with the skirt portions [2 at' longitudinally .as well as at transversely or circumferentially spaced points, and in accordance therewith the legs l5 and I6 are curved outwardly to provide skirt-engaging portions l8 and I9 which are designed to grip the skirt portions l2 adjacent the cross slot 8. It will be noted, as shown in Figure 1, that with the segment M and gripping portions i8 and H9 in proper engagement with the skirt, the legs Hand 56 will be obliquely disposed relative'to the pis ton axis and'at the same time they will be in a position to engage the juncture points aforesaid. In this manner when the 'member has been operativelyinserted in the piston and forced sufiiciently inwardly therein with the parts engaged as above, the segment and gripping portions l8 and I!) will be pressed against the skirt with a force proportional to tension set up by the wedging of the legs against the bearings and contiguous parts. Thus the amount of expansion of the skirt portions can be readily varied by inserting the member into the piston to the proper degree. It will benoted that the legs of the member slope obliquely not only as aforementioned, but as clearly shown in Figure 3, they converge toward one another as they recede from the segment. In this way, on insertion of the member in the piston, tension will be set up in the member both as a' result of deflection of the legs by engagement with the bearings and by engagement with the transverse side portions ll. It will be seen that the wedging action of the legs against the bearings 9 causes the entire member to be forced directly against the piston portions 02, while on the other hand the wedging of the legs against the side portions ll, coupled with the anchoring of the legs against the bearings 9, produces a contraction of the legs toward one another and a corresponding protrusion of the gripping portions l8 and I9 and the skirt-engaging portion of the segment directly against said portions l2. Thus as readily evident, an expanding pressure of considerable extent may be impressed on the skirt by the operative positioning of the member within the piston. At the same time, owing to the form and manner of engagement of the parts of the member with the piston, said force of expansion will be sufiiciently yielding and resilient to prevent uneven strain on the piston portions and sticking and undue wear of the piston and engaging portions of the cylinder.

An important feature of the expanding member of my invention is that it effects the expansion of the skirt portions by application of forces in the very direction toward which the protrusion of the skirt is desired. In other words expansion is not brought about by merely spreading the skirt portions apart such as solely by application of opposed forces more or less parallel to the wrist pin axis. An expansion produced by the latter method effects not only a protrusion of the slitted portions but in addition causes an undesirable and harmful expansion of the piston in line with the wrist pin axis. In view of the foregoing, the type of piston desirable for use with my member is the conventional, that is, where only a small amount of expansion of the latter type is permitted and furthermore, in keeping with such desirability, the slit 8 is kept short. Thus when my member is operatively inserted in a piston so formed, as no appreciable expansion maybe effected in line with the pin axis, the principal outlet for the force is directly against the portions l2, and since the engagement of the skirt with the segment and gripping portions occurs at or adjacent the slit 1, the expansion of the skirt portions l2 will be efiected evenly in each portion, and in each instance the expansion will be substantially increasingly greater as the slit is approached. In this way the cross section of the piston will be made to conform to the oval shape of the cylinder and the retention of the piston 'in the cylinder in proper centralized position will be assured.

Preferably, and as clearly shown in Figure l, the gripping portions 18 and I9 are inclined toward the segment and their free ends are cutofi' or otherwise formed to provide a sharp or pointed extremity 2| which is arranged in the operative position of the member in the piston to constitute the point of bearing with the inner face of the skirt. It will be evident that when the member is firmly wedged in position the points 2| will partially penetrate the piston wall and thereby cause the member to be effectively locked in proper position in the piston. It will also be evident that while the points M will not materially resist the insertion movement of the member, they will most eifectively resist withdrawal since a pull upon the segment will cause the legs to fulcrum on the bearings 9 and thereby force the points more forcibly into the piston wall. Removal of the member may however be readily accomplished when desired, such as by the insere tion of an instrument against the legs to keep the points spaced from the wall while the member is. pulled out through the open end of the piston.

A slightly modified form of the expander is illustrated in'Figure 5. This form of the invention differs principally from the embodiment above disclosed in the formation of its gripping portions l8 and I9 and comprises, in common with the first expander, a resilient wire 2 having side portions 15 and it arranged to engage with the bearings 9 and having an arcuate portion i l connecting the ends of and bent from the plane of said side portions and arranged to bear against and radially expand the portion I2 of the piston. The expander is positionedin the piston with .the free ends l8 and iii of the wire extending towards the open end 6 of the piston and with these ends slightly outwardly curved and each reduced to' a sharpened edge to effect a penetration into the side walls of the pistonskirt incident to a withdrawal movement of the expander. While this arrangement effectively locks the expander in 1312!.38, a removal of the same may be readily accomplished, as with the expander in the above embodiment, by springing the ends l8 and I9 toward each other and spaced from the piston side walls with the use of a plier or other instrument while withdrawing the wire from the open end of the piston.

It will now be clear that the expander means of my invention is well adapted to the accomplishment of the objects hereinbefore referred to.

I claim:

1. An expander for a hollow piston having a longitudinally extending split portion in the skirt thereof, comprising a resilient wire arranged for mounting in said piston and having a curved side disposed to bear against and radially expand said portion, an end of said wire being sharply defined and arranged with the wire operatively mounted in the piston to dig in to the inner wall of the piston to hold the wire against displacement.

2. In an expander for a hollow piston having a longitudinally extending split portion in the skirt thereof and provided with a pair of diametrically opposed projections on the inner walls thereof for securing connecting means for the piston, a resilient wire comprising a pair of side portions arranged for engagement with said projections, and a portion connecting and bent from the plane of said side portions and arranged to bear against and radially expand said split portion.

3. An expander for a hollow piston having a. longitudinally extending split portion in the skirt thereof and provided with a pair of diametrically opposed projections on the inner walls thereof for securing connecting means to the piston, comprising a resilient substantially U shaped wire including a pair of substantially parallel side portions arranged for engagement with said projections, and a curved portion connecting the ends of and bent at substantially .right angles from the plane of said sideportions and arranged to bear against and radially expand said split portion.

4. An expander for a hollow piston having a longitudinally extending split portion in the skirt thereof and provided on the inner walls thereof with a pair of inwardly projecting connecting rod bearings and comprising a resilient substantially U shaped wire including a pair of side portions arranged to be wedged between and to engage with the outer sides of said bearings, a curved portion connecting the ends of and bent from the plane of said side portions and arranged to bear against and radially expand said split portion, and hook-shaped portions formed at the other ends of said side portions and provided with sharpened end edges disposed to dig into the side walls of the piston incident to a withdrawal movement of the wire therefrom.

5. An expander for a hollow piston having a longitudinally extending split portion in the skirt thereof and provided on the inner walls thereof with a pair of inwardly projecting connecting rod bearings and comprising a resilient substantially U-shaped wire including a pair of side porttions arranged to be wedged between and to engage with the outer sides of said bearings, a curved portion connecting the ends of and bent from the plane of said side portions and arranged to bear against and radially expand said split portion, and sharpened portions provided at the free ends of said wire extending towards the lower open end of said piston and arranged to dig into the side walls of the piston incident to a withdrawal movement of the wire therefrom.

CHARLES F. JOHNSTON. 

